The photo above shows a drawing of a specimen retrieved from a quarry near Oxford in 1676. It is the end of the femur, and was named by British naturalist Richard Brookes after what he thought it looked like.

It was given the name Scrotum humanum in 1763 but it didn't catch on; it was renamed Megalosaurus by Reverand Buckland in 1824. The word dinosaur wasn't coined until sixteen years later.

Found in the "Nutty Nomenclature" subsection of the link at Null Hypothesis, which also includes a small brown moth whose official scientific name is "Eubetia bigaulae."